The audible ringing pattern of an incoming call is strictly fixed by and dependent upon the pattern of direct or indirect ringing signals placed upon the subscriber's line by the telephone switching office. Unfortunately, the standard ring of most telephones can be unpleasant, and, in environments in which the telephone rings frequently, such ringing often becomes irritating. This is due in part to the poor quality of the audio output devices which are in use today.
The invention and use of stereo synthesizers is known to the public. For example, U.S. Pat. No. 4,841,572 issued to Klayman in 1989 discloses a stereo image enhancement system in which difference signal components in relatively quieter difference signal frequency bands are boosted to provide an improved stereo image. Such a system could greatly enhance and improve the quality of audio announcements of incoming telephone calls.
However, another problem with standard ringing is that the tone of most telephones is rather shrill, and would thus be annoying even with improved ring quality. In addition, the audible ringing signal is virtually identical for each telephone, which makes it extremely difficult to determine which telephone is ringing in settings, such as offices or households, with more than one phone line.
Thus, there is a need for a device that allows each user to select an output to replace the standard ring tone of a telephone. Such a device would also include a stereo enhancement system, to improve the quality of the selected output. The present invention fulfills these needs and provides further related advantages.